Cationic porphyrin-based covalent organic frameworks for enhanced phototherapy and targeted chemotherapy of bacterial infections

Bacterial infections significantly impede wound healing and threaten global public health. Porphyrin covalent organic frameworks (COFs) have shown promise as phototherapy antibacterial materials. However, the inherent π-π stacking interactions between the monomers also lead to aggregation and quenching of photosensitizers, thereby reducing the production of singlet oxygen (1O2) and compromising their antibacterial efficacy. Herein, we designed and prepared a novel cationic porphyrin-based COFs nanoplatform (TAPP-VIO), utilizing photosensitive TAPP and cationic VIO as structural units. This multifunctional nanoplatform is specifically tailored for targeted phototherapy and chemotherapy against bacterial infections. Upon irradiation, TAPP unit in TAPP-VIO generates heat and 1O2, which effectively disrupt bacterial structure and cause cell death. The incorporation of VIO unit introduces electrostatic repulsion between layers, mitigating π-π stacking effects and enhancing 1O2 production. Additionally, the positive charge imparted by the VIO unit enables TAPP-VIO to bind efficiently to negatively charged bacterial surfaces, immobilizing the bacteria and reducing their motility, thereby improving the overall efficacy of phototherapy. Under identical experimental conditions and concentrations, TAPP-VIO exhibits a 1O2 generation capacity that is 179 % higher than that of nonionic porphyrin COF. Moreover, the temperature increase induced by TAPP-VIO is 85 % of that observed with nonionic porphyrin COF (TAPP-MMA-Da), which is conducive to enhancing the phototherapeutic effects while minimizing heat-induced damage to healthy tissues. In summary, our study presents a straightforward approach to developing non-antibiotic antibacterial nanoagents, and the as-prepared TAPP-VIO is a promising candidate drug suitable for clinical trials in the future.

Confining metal nanoparticles and nanoclusters in covalent organic frameworks for biosensing and biomedicine

Metal nanoscale particles, primarily including metal nanoparticles (MNPs) and nanoclusters (MNCs), have garnered substantial interests owing to their unique electronic configurations and distinct physicochemical properties. However, practical applications are frequently constrained by their limited stability and aggregation tendency. Covalent organic frameworks (COFs), featuring highly ordered periodic architectures, have emerged as ideal porous matrices for hosting metal nanoparticles. The resulting metal-embedded COFs synthesized through adsorption methods (M/COFs) or in-situ reduction (M@COFs) not only mitigate nanoparticle aggregation and enhance stability but also demonstrate synergistic effects that generate enhanced or novel functionalities, significantly broadening their application potential. This review firstly examines adsorption-based synthesis strategies for M/COFs through physical and chemical approaches. Subsequently, we analyze in-situ reduction methods for M@COFs, categorizing them by reduction pathways: deposition, impregnation-pyrolysis, and "one-step" synthesis. Special attention is given to an emerging pore wall engineering strategy within in-situ reduction approach. The biosensing and biomedical applications of metal-embedded COFs are systematically examined, highlighting their comparative advantages over conventional nanomaterials in sensing and antimicrobial applications. While metal-embedded COFs remain in their developmental infancy and face considerable challenges, the controlled synthesis of multifunctional variants promises transformative potential across biomedical domains.

Asymmetric heterogeneous catalysis using crystalline porous materials

Asymmetric catalysis has emerged as a pivotal strategy in the synthesis of chiral compounds, offering significant advantages in selectivity and efficiency. In recent years, heterogeneous catalysis has become a focal point in the fields of organic synthesis and materials science due to continuous advancements in science and technology, especially the use of crystalline porous materials (CPMs) as catalysts. This review summarizes recent advances in using CPMs, such as metal-organic frameworks (MOFs), covalent organic frameworks (COFs) and zeolites, as promising supports for asymmetric catalysts. These materials provide high surface areas, tunable porosity, and the ability to host active catalytic sites, which enhance reaction rates and selectivity. In this review, we summarize the stereostructural properties of chiral CPMs to guide the future design of asymmetric heterogeneous catalysts and the study of catalytic mechanisms. Moreover, we discuss various strategies for incorporating catalytic moieties into these frameworks, including direct synthesis, post-synthesis modification and induced synthesis methods. Additionally, we highlight recent examples where CPMs have been successfully applied in asymmetric transformations, examining their mechanistic insights and the role of substrate diffusion in achieving high enantioselectivity. This review concludes with a perspective on the challenges and future directions in this rapidly evolving field, emphasizing the need for further integration of advanced artificial intelligence techniques and design principles to optimize the synthesis and catalytic performance of chiral CPMs.

Melamine sponge loaded anionic covalent organic framework by sodium alginate cross-linking for selective dye removal with high adsorption capacity and reusability

Ionic dyes are widely used and emitted in large quantities by modern industries. It is of great importance to develop efficient and practical adsorbent materials for the removal of such pollutants. Ionic covalent organic frameworks (COFs) with charged pore environments and stable backbone structures are excellent candidates for dye adsorbents. To improve the drawbacks of COF powder, which is not easy to be recycled and prone to secondary pollution, we report an effective strategy to prepare the composite material by immobilizing dispersed anionic COF on melamine foam sponge (MF@COF). Sodium alginate cross-linking method is developed as a powerful combination of COF and MF, with no powder falling off during adsorption. The composite material can quickly adsorb dyes, and the removal rate of cationic dyes can reach >99 % in 10 min; at the same time, it can selectively separate anionic dyes. The adsorption capacity of MF@COF for methylene blue (MB), crystal violet (CV), and malachite green (MG), was 947 mg g-1, 466 mg g-1 and 1689 mg g-1 in terms of the weight of COF, respectively. Compared with using the COF powder alone, the adsorption capacity of the composite material has been improved to a certain extent, with MB's adsorption capacity increasing by 6.16 %. Furthermore, MF@COF composite showed its practicality in practical water adsorption tests and could be recycled >5 times, which makes it a simple and practical adsorbent for water pollution control.

Exceptional quenching properties of tetrazine-based organic frameworks for fluorescently labeled nucleic acids and their applications in sensing

Covalent organic frameworks (COFs) have garnered significant attention due to their unique properties, such as high surface area, porosity, chemical stability, and sustainability, which enable a wide range of applications in recent years. In this study, tetrazine-based organic frameworks, named TzF-9, were investigated for their ability to quench fluorescence in nucleic acids labeled with fluorophores. The experimental results demonstrated that TzF-9 effectively quenched the fluorescence of fluorophore-labeled single-stranded deoxyribonucleic acid (ssDNA) probes with more than six bases. Notably, the quenching process was rapid, reaching equilibrium in just about three minutes to achieve a high quenching efficiency (∼95%). Significantly, its excellent quenching ability is retained across a wide pH range. Furthermore, fluorescent dyes, including fluorescein (FAM), cyanine dye 3 (Cy3), and 6-carboxy-X-rhodamine (ROX), labeled on long ssDNA probes, were efficiently quenched, indicating that TzF-9 can function as a universal fluorescence quencher. In addition, the quenching efficiency of TzF-9 for short ssDNA and double-stranded DNA (dsDNA) probes was significantly lower than for long ssDNA probes. Taking advantage of these distinct quenching efficiencies for DNA probes with different structures, TzF-9 was employed as a sensing platform for detecting ssDNA and nuclease activity, exhibiting good selectivity and high sensitivity. With its combination of strong quenching ability and high stability, TzF-9 presents a promising quencher for biosensing applications.

Semiconducting Covalent Organic Frameworks

Semiconductors form the foundational bedrock of modern electronics and numerous cutting-edge technologies. Particularly, semiconductors crafted from organic building blocks hold immense promise as next-generation pioneers, thanks to their vast array of chemical structures, customizable frontier orbital energy levels and bandgap structures, and easily adjustable π electronic properties. Over the past 50 years, advancements in chemistry and materials science have facilitated extensive investigations into small organic π compounds, oligomers, and polymers, resulting in a rich library of organic semiconductors. However, a longstanding challenge persists: how to organize π building units or chains into well-defined π structures, which are crucial for the performance of organic semiconductors. Consequently, the pursuit of methodologies capable of synthesizing and/or fabricating organic semiconductors with ordered structures has emerged as a frontier in organic and polymeric semiconductor research. In this context, covalent organic frameworks (COFs) stand out as unique platforms allowing for the covalent integration of organic π units into periodically ordered π structures, thus facilitating the development of semiconductors with extended yet precisely defined π architectures. Since their initial report in 2008, significant strides have been made in exploring various chemistries to develop semiconducting COFs, resulting in a rich library of structures, properties, functions, and applications. This review provides a comprehensive yet focused exploration of the general structural features of semiconducting COFs, outlining the basic principles of structural design, illustrating the linkage chemistry and synthetic strategies based on typical one-pot polymerization reactions to demonstrate the growth of bulk materials, nanosheets, films, and membranes. By elucidating the interactions between COFs and various entities such as photons, phonons, electrons, holes, ions, molecules, and spins, this review categorizes semiconducting COFs into nine distinct sections: semiconductors, photoconductors, light emitters, sensors, photocatalysts, photothermal conversion materials, electrocatalysts, energy storage electrodes, and radical spin materials, focusing on disclosing structure-originated properties and functions. Furthermore, this review scrutinizes structure-function correlations and highlights the unique features, breakthroughs, and challenges associated with semiconducting COFs. Furnished with foundational knowledges and state-of-the-art insights, this review predicts the fundamental issues to be addressed and outlines future directions for semiconducting COFs, offering a comprehensive overview of this rapidly evolving and remarkable field.

Anisotropic Thermal Conductivity in Imine-Linked Two-Dimensional Polymer Films Produced by Interfacial Polymerization

Anisotropic thermal transport was measured in imine-linked two-dimensional polymer (2DP) films that were prepared by interfacial polymerization. Measurements of both in-plane (k∥) and cross-plane (k⊥) thermal conductivities relied on preparing free-standing 2DP films that were readily transferred for different measurement configurations. We polymerized two 2DP (Per-PDA and TAPPy-PDA) films at a liquid-liquid interface. These polycrystalline, imine-linked 2DP films are 100-200 nm in thickness and were measured by frequency domain thermoreflectance to extract k⊥ and a suspended calorimetric platform technique to evaluate k∥. We find that k∥ is larger than k⊥ in both materials at room temperature, leading to anisotropy ratios (k∥/k⊥) as high as 2.3. We attribute this behavior to the fact that the stiff, in-plane covalent bonds of 2DPs transport heat more effectively than the flexible, supramolecular cross-plane interactions. Variable-temperature measurements revealed a positive correlation between temperature and thermal conductivity, which we attribute to phonon scattering from grain boundaries and defects in the polycrystalline 2DP films. Molecular dynamics simulations of pristine crystals predict larger thermal conductivities and anisotropy ratios exceeding 7. The simulations suggest that as higher quality 2DP films become available, higher thermal conductivities and anisotropy ratios will also manifest.

A multi-stage COF membrane column system for enhanced Yb/Lu separation

This study introduces an innovative multi-stage membrane column separation system that combines membrane and column separation technologies, utilizing a COF membrane as the packing material. This approach achieves a superior separation factor and a reduced elution volume for Yb3+/Lu3+ separation, offering a new approach to address challenges in column separation.

One-Dimensional Covalent Organic Frameworks: From Design, Synthesis to Applications

As an important branch of the covalent organic frameworks (COFs) family, one-dimensional COFs (1D COFs), which are formed by the ordered arrangement of confined covalent bonds in one dimension and non-covalent interactions (van der Waals force, π-π interactions, and hydrogen bonds) in the vertical two and three dimensions has aroused much attention. Compared with two-dimensional (2D)/three-dimensional (3D) COFs, 1D COFs behaved more easily dispersing and had more opportunities for active sites exposure due to their weaker interchain/interlayer interaction, modified nonlinear edge, and pore structures. These features make them have great application potential in many fields, including catalysis, energy storage, adsorption, sensing, and others. In this minireview, we highlight the state-of-the-art advances of 1D COFs in the structure design principles of building blocks, synthesis strategies, and their related applications. Furthermore, we present an in-depth outlook on the challenges and opportunities faced by 1D COFs, aiming to offer insights for future studies in this intriguing and significant research field.

Post-oxidation of all-organic electrocatalysts to promote O-O coupling in water oxidation

Covalently bonded metal-free electrocatalysts exhibit significant potential for sustainable energy technologies, yet their performances remain unsatisfactory compared with metal-based catalysts. Herein, we propose an all-organic electrocatalyst, MEC-2, that conforms to the infrequent oxide path mechanism in alkaline oxygen evolution reaction through post-oxidation modification. MEC-2 achieves an intrinsic overpotential of 257.7 ± 0.6 mV at 10 mA·cm-2 and possesses durability with negligible degradation over 100,000 CV cycles or 250 h of operation at 1.0 A·cm-2, being comparable to the advanced metal-based OER electrocatalysts. The 18O-labeled operando characterization and theoretical calculations unveil that post-oxidation modification enhances the electron affinity to OH intermediates, and adjusts the adsorption configuration and proximity distance of O intermediates, thereby promoting direct O-O radical coupling. In this work, we show a fresh perspective for understanding the role of non-metallic elements/functional groups in electrocatalysis, and to a certain extent, narrows the gap between all-organic electrocatalysts and metal-based electrocatalysts.

Covalent organic framework-based surface plasmon-enhanced fluorescence sensing for real-time monitoring of cell apoptosis

The complex physiological environment of living organisms is a major hurdle for in situ monitoring of vital cellular activities. Here, we propose that the surface plasmon-coupled emission (SPCE) biointerface sensing system prepared by modifying covalent organic frameworks (COFs) on metal substrates, can be a powerful tool for biointerface sensing. We have successfully developed a novel pH-responsive fluorescent COF nanoprobe, where fluorophores were precisely post-modified into intrinsically enriched chemically reactive sites within the nanoporous structure. A graphene oxide-assisted assembly strategy was employed to facilitate the robust integration of COFs onto the Ag film. Remarkably, the resulting COF-modified biosensing platform achieves a 40-fold directional fluorescence enhancement in directional fluorescence, attributed to the synergistic coupling between the near-field excited fluorophore dipole, Ag nanofilm and π-conjugated graphene oxide. By precisely controlling the penetration depth of the evanescent through angular modulation of incident light, selective detection of the extracellular and intracellular information can be realized. This allows us to construct a stable, fluorescence-enhanced biosensor chip based on surface plasmon coupling for accurate in situ monitoring of extracellular pH changes during apoptosis.

Turing-Structured Covalent Organic Framework Membranes for Fast and Precise Peptide Separations

Turing structures have emerged as promising features for separation membranes, enabling significantly enhanced water permeation due to their ultra-permeable internal cavities. So far, Turing structures are constrained by the highly cross-linked and heterogeneous porosities, impeding them from the application of molecular separations requiring loose but regular pore structures. This work reports a covalent organic frameworks (COFs) membrane with nanoscale striped Turing structures for fast and precise molecular separations. Porous and hydrophilic modulation layers based on metal-polyphenol chemistry are constructed on polymeric substrates, which are capable of enhancing the uptake and controlled release of the activator of amines during synthesis. The appropriately reduced diffusion rate triggers the phenomenon of "local activation and lateral inhibition" arising from thermodynamic instability, creating Turing structures with externally striped and internally cavitated architectures. The Turing-type COF membranes exhibit a water permeance of 45.0 L m-2 h-1 bar-1, which is approximately 13 times greater than the non-Turing membranes, and an ultrahigh selectivity of up to 638 for two model peptides. This work demonstrates the feasibility that Turing structures with ultra-permeable internal cavities can be created in COF membranes and underscores their superiority in molecular separations, including but not limited to high-value pharmaceuticals.

Recent Advances in the Application of Covalent Organic Framework-Based Ionic Conductors in Proton Exchange Membrane Fuel Cells

Covalent organic frameworks (COFs), known for their tunable porosity and functional versatility, have demonstrated exceptional ionic conductivity in proton exchange membrane fuel cells (PEMFCs). This review summarizes recent advancements in COF-based materials for PEMFC applications, emphasizing their roles as intrinsic proton conductors, host matrices for proton carriers, and additives in composite ionomers/membranes. Key strategies such as pore engineering, functional group modification, and hybrid designs with polymers are analyzed to highlight their influence on proton conductivity and mechanical stability. Recent developments reveal that functionalized COFs can achieve proton conductivities exceeding 0.89 S cm-1 at 90 °C under 100% relative humidity (RH), comparable to commercial Nafion membranes. Additionally, COF-modified ionomers applied to catalyst layers have enabled fuel cells to achieve peak power densities 1.6 times higher than those without COF incorporation. Despite these advancements, challenges persist in terms of membrane durability, scalability, and performance under low humidity or high-temperature conditions. Future research should prioritize structural optimization, interfacial compatibility, and cost-effective synthesis methods to fully realize the potential of COFs in next-generation PEMFCs. This review underscores the transformative potential of COFs in addressing the critical limitations of traditional proton-conducting materials, paving the way for innovative solutions in fuel cell technology.

Recent Progress of Covalent Organic Frameworks-Based Materials Used for CO2 Electrocatalytic Reduction: A Review

The excessive CO2 emissions from human activities severely impact the natural environment and ecosystems. Among the various technologies available, electrocatalytic CO2 reduction is regarded as one of the most promising routes due to its exceptional environmental friendliness and sustainability. Covalent organic frameworks (COFs) are crystalline, porous organic networks that are formed through thermodynamically controlled reversible covalent polymerization of organic linkers via covalent bonding. These materials exhibit high porosity, large surface area, excellent chemical and thermal stability, sustainability, high electron transfer efficiency, and surface functionalization capabilities, making them particularly effective in electrocatalytic CO2 reduction. First, this review briefly introduces the fundamental principles of electrocatalysis and the mechanism of electrocatalytic CO2 reduction. Next, it discusses the composition, structure, and synthesis methods of COF-based materials, as well as their applications in electrocatalytic CO2 reduction. Furthermore, it reviews the research progress in this field from the perspective of different types of COF-based catalysts. Finally, in light of the current research status, the development prospects of COF-based catalysts are explored, providing a reference for the development of more efficient and stable COF electrocatalysts for CO2 reduction.

Bayesian Optimized Crystallization of a Hydroxamate-Functionalized Covalent Organic Framework for Enhanced Uranyl Uptake

To address the synthetic challenge of covalent organic frameworks (COFs), especially those with interfering functional groups, a Bayesian optimization (BO) centered approach is developed and implemented. Specifically, the crystallinity index for a well-known TAPB-PDA COF is improved by ≈80% via a one-round proof-of-concept BO. For a more complicated task toward the preparation of hydroxamate-functionalized TpPa COF, where improvement of both crystallinity and selectivity (against a crystalline byproduct) is needed, an efficient protocol comprising 6 BO iterations (with 5 experiments each) from an initial 64-experiment dataset is successfully developed. The functional COF, namely SUM-99 (SUM = Sichuan University Materials), with enhanced crystallinity, is subsequently demonstrated to be an effective, reversible, and selective sorbent for aquatic uranyl uptake. The importance of improved crystallinity, reflecting the power of BO, is showcased by a 23.7% increase in uranyl adsorption capacity. Therefore, the BO protocol and toolkit is presented for the efficient evolution of COF synthetic conditions, toward higher crystallinity and enhanced performances for downstream applications.

Reverse filling approach to mixed matrix covalent organic framework membranes for gas separation

Mixed-matrix membranes that combine the merits of polymer and filler materials offer high potential for molecular separations, but precisely engineering the filler phase structure to give full play to the role of filler materials remains challenging. Herein, we explore a reverse-filling approach to fabricate mixed-matrix membranes with continuous and vertically penetrating covalent organic framework channels for CO2 separation. Covalent organic framework nanosheets as building blocks are pre-assembled into a robust and vertically oriented covalent organic framework scaffold via ice templating method, with the subsequent polyimide filling into the scaffold. The scaffold inherits the intrinsic CO2-philic pore structure of nanosheets, which serves as fast and selective CO2 transport channels in the membrane. The resulting membrane exhibits high CO2 permeability of 972 Barrer and CO2/CH4 selectivity of 58, along with long-term stability and scale-up capability. This approach may stimulate the thinking about how to design advanced mixed-matrix membranes.

Two-Dimensional Heteropore Covalent Organic Frameworks: From Construction to Functions

ConspectusCovalent organic frameworks (COFs) represent a fascinating class of crystalline porous polymers constructed from organic building blocks linked by covalent bonds. Benefiting from their high crystallinity, large surface area, and ease of functionalization, COFs have demonstrated significant potential across various fields, including gas adsorption, luminescence, sensing, catalysis, energy storage, nanomedicine, etc. In the first decade of COF development, only those with homogeneous porosity have been constructed, and thus, their topological structures are quite limited. An exciting progress in the field of COFs is the emergence of two-dimensional (2D) COFs with hierarchical porosity, known as heteropore COFs, which have garnered considerable attention in recent years. Heteropore COFs are deliberately designed to integrate different types of pores into a single framework, resulting in heterogeneous porosity that imparts captivating properties and functions. Compared to their homopore counterparts, heteropore COFs offer a compelling platform for creating hierarchically structured porous materials, thanks to their distinctive multicompartment architectures and different pore environments. Since we achieved the construction of the first heteropore COF featuring both micropores and mesopores in 2014, substantial advancements have been achieved in the realm of heteropre COFs over the past decade, considerably increasing the topological diversity of 2D COFs. In this Account, we summarize our contributions to the development of 2D heteropore COFs. First, we review representative design strategies for the construction of 2D heteropore COFs, including the angle-specific-vertex, heterostructural-mixed-linker, multiple-linking-site, and desymmetrization-design strategies and their combinations as well as the dynamic covalent chemistry-mediated linker exchange strategy. Based on these strategies, heteroporous frameworks with two, three, and four different kinds of pores and different types of linkages have been successfully fabricated. Next, we discuss the properties and applications of heteropore COFs, including those shared with their homopore counterparts and unique ones originating from their hierarchical porous structures. Our research has shown that heteropore COFs have inherited the common features from their homopore counterparts and exhibited application potentials in gas adsorption, chemical sensing, environmental remediation, etc. More importantly, the multicompartment architecture and heterogeneous pore environment of heteropore COFs offer distinct benefits, for which exclusive applications and unique properties of heteropore COFs distinct from those of homopore COFs have been demonstrated. Finally, we highlight the current challenges and future directions of heteropore COFs, with an emphasis on the development of structural design and synthetic methodologies, precise structural characterization, and the exploration of unique properties and advanced applications. We believe that this Account will offer valuable insights into the design and synthesis of COFs with heteroporous structures, thereby accelerating their applications across a wide range of interdisciplinary research areas.

Overcoming Boundaries: Towards the Ambient Aqueous Synthesis of Covalent Organic Frameworks

The synthesis of covalent organic frameworks (COFs) has traditionally been carried out under strict solvothermal and anaerobic conditions. The utilization of organic solvents in such reactions not only carries significant costs but also imposes a great burden on the environment. The fabrication of COFs using alternative synthetic pathways has, therefore, seen rapid development in recent years and much attention has been placed on green and sustainable methods in particular. The synthesis of COFs in purely aqueous media, however, remains challenging due to the delicate nature of the chemical reactions and the crystallization process in water. This mini-review discusses different synthetic strategies for the construction of crystalline COFs in aqueous media and offers a perspective on the future development of facile COF synthesis in ambient conditions.

Crystalline, Porous Figure-Eight-Noded Covalent Organic Frameworks

Figure-eight macrocycles represent a fascinating class of π-conjugated units characterized by unique aesthetics and non-contact molecular crossing at the center. Despite progress in synthesis over the past century, research into inorganic, organic, and polymeric figure-eight materials remains in its infancy. Here we report the first examples of figure-eight covalent organic frameworks by condensing figure-eight knots to create extended porous figure-eight π architectures. A distinct feature is that polymerization interweaves figure-eight knots into double-decker layers, which upon supramolecular polymerization organize well-defined layer frameworks. The figure-eight frameworks exhibit a band gap of 2.3 eV and emit bright orange florescence with benchmark quantum yields. Remarkably, the donor-acceptor figure-eight skeletons convert the figure-eight knots into reduction centers and the linkers into oxidation sites upon light irradiation, enable charge transport and accumulation through π columns, while the built-in hydrophilic micropores allow rapid water and oxygen delivery via capillary effect. With these distinct features, the figure-eight frameworks function as a photocatalyst to produce hydrogen peroxide at high rate and efficiency with water/saltwater, oxygen/air, and light as sole inputs. This work paves a way to a new class of molecular frameworks, underpinning the study of well-defined figure-eight materials to explore unprecedented structures and functions so far we untouched.

Soluble Covalent Organic Frameworks as Efficient Lithiophilic Modulator for High-Performance Lithium Metal Batteries

Lithium metal batteries (LMBs) are regarded as the potential alternative of lithium-ion batteries due to their ultrahigh theoretical specific capacity (3860 mAh g-1). However, severe instability and safety problems caused by the dendrite growth and inevitable side reactions have hindered the commercialization of LMBs. To solve them, in this contribution, a design strategy of soluble lithiophilic covalent organic frameworks (COFs) is proposed. By introducing polyethylene glycol as the side chains, two COFs (CityU-28 and CityU-29) not only become soluble for the facile coating technique, but also can facilitate the lithium-ion migration in batteries. Furthermore, when coated on the lithium anode of LMB, both COFs can act as artificial solid electrolyte interphase to prevent dendrite growth thus enabling the long-term stability of the cells. Notably, the symmetric CityU-29@Li cell can work for more than 5000 h at a current density of 2 mA cm-2 and an areal capacity of 1 mAh cm-2. A remarkable capacity retention of 78.9 % after 1500 cycles and a Coulombic efficiency of about 99.9 % at 1.0 C can also be realized in CityU-29@Li||LiFePO4 full cell. This work could provide a universal design strategy for soluble COFs and enlighten their application in diverse scenarios, especially energy-related fields.

1,3,5-Triformylphloroglucinol Derived β-Ketoenamine-Linked Functional Covalent Organic Frameworks with Enhanced Crystallinity and Stability-Recent Advances

Crystallinity, stability, and complexity are significant factors to consider in the design and development of covalent organic frameworks (COFs). Among various building blocks used, 1,3,5-triformylphloroglucinol (Tp) is notable for enhancing both crystallinity and structural stability in COFs. Tp facilitates the formation of β-ketoenamine-linked COFs through keto-enol tautomerism when reacted with aromatic amines. This review article examines the stability, crystallinity, and flexibility of synthetic methodologies involving Tp-based COFs, while highlighting their recent applications. We emphasize the critical roles of non-covalent interactions and keto-enol tautomerism in achieving high levels of crystallinity and stability. Additionally, the diverse and straightforward synthesis methods available for Tp-based COFs contribute to the prevalence of 1,3,5-triformylphloroglucinol in COF development. We conclude by addressing the challenges and future prospects in this area, underscoring the significant potential of Tp-based COFs for environmental and energy-related applications due to their exceptional structural tunability and functionality.

Fluorinated Covalent Organic Framework Antifouling Nanofiltration Membranes Through Defect Engineering

Covalent organic framework (COF) membrane holds great promise in water treat-ment. Improving the antifouling property of COF membrane is critical for practical application while rare investigations have been reported. Grafting fluorinated chains on the COF membrane surface is expected an effective strategy but quite challenging due to the lack of grafting sites. In this work, the defect engineering strategy is adopted to generate free amino groups as grafting sites through the Schiff-base reaction between amine monomer and mixed aldehyde monomers, then perfluoroalkyl chains are grafted on the COF membrane surface through the reaction between the free amino groups and the perfluorooctanoyl chloride. The content of perfluoroalkyl chains can be regulated and optimized by controlling the amount of free amino groups. The fluorinated COF membrane shows superior antifouling performance with a significantly increased flux recovery ratio and reduced flux decline ratio against oil/water emulsions and humic acid (FRR ≈ 98%, DRt = 10%). Furthermore, the fluorinated COF membrane exhibits high water permeance up to ≈115 L m-2 h-1 bar-1 while acquiring a high salt/dye selective factor. This work affords an effective approach to the development of antifouling, high-separation-performance COF membranes, and other kinds of organic molecular sieve membranes.

Interface-Confined Catalytic Synthesis of Anisotropic Covalent Organic Framework Nanofilm for Ultrafast Molecular Sieving

Covalent organic frameworks (COFs) have emerged as prominent membrane materials for efficiently fractionating organic molecules and ions due to their unique pore structure. However, the fabrication of free-standing COF nanofilms with high crystallinity remains an arduous undertaking, and feasible methods that can enable precise control over the film microstructure are barely reported. This work conceives an exquisite interface-confined catalytic strategy to prepare Tp-BD(OH)2 COF nanofilm with an anisotropic structure analogously to conventional polymeric membranes. Experimental data and molecular simulations reveal that the hydroxyl groups on the framework substantially capture and anchor the acid catalyst through hydrogen bonding interactions at the incipient stage of interfacial polycondensation, instigating confined catalysis and self-termination reaction at the interface. The distinctive asymmetric structure endows the Tp-BD(OH)2 COF nanofilm with a record-breaking pure water permeance of 525.3 L m-2 h-1 bar-1 and unprecedented dye/salt selectivity of 648.6, surpassing other reported COF films and state-of-the-art nanofiltration membranes, as well as enduring structural durability and chemical stability. The implemented interface-confined catalysis strategy opens up a new avenue for regulating the COF nanofilm microstructure and holds broad prospects for the rational design of high-performance membranes for sustainable water purification and treatment.

Protonation of Nitrogen-Containing Covalent Organic Frameworks for Enhanced Catalysis

Covalent organic frameworks (COFs) are a class of porous crystalline materials with ordered structures and tunable properties, which have been widely explored in catalysis, sensing, gas storage, and separation. Among various post-synthetic modifications, protonation emerges as a simple yet effective strategy to fine-tune the properties of nitrogen-containing COFs, thereby enhancing their catalytic performance. This concept article highlights the contribution of protonation on the mass transfer kinetics, charge distribution, photo-response, charge transfer, and other properties related to photocatalysis and electrocatalysis. The applications of protonated COFs are explored in catalytic processes including hydrogen evolution, CO2 reduction, H2O2 synthesis, and singlet oxygen generation. We also emphasize the necessity of considering the protonation process when nitrogen-containing COFs are applied in acidic environments to accurately reveal the structure-activity relationship. By analyzing recent advancements in protonated COFs, this article underscores the potential and challenges of protonation as a powerful tool for advancing COF-based catalytic systems.

Preparation and Quaternization of Poly (Styrene-Divinylbenzene) Microspheres Loaded With p-Phenylenediamine-1,3,5-Triformylphloroglucinol Nanoparticles and Utilized as an Anion Exchanger

Covalent organic framework (COF) has been popularly utilized to prepare chromatographic stationary phases due to its a great diversity of composition, unique structure, easy of modification, and so forth. However, the irregular shape and nanometer size scale of most COF materials greatly hinders their direct utilization as chromatographic column packing. Herein, poly (styrene-divinylbenzene) loaded with p-phenylenediamine-1,3,5-triformylphloroglucinol nanoparticles that derived from p-phenylenediamine and 1,3,5-triformylphloroglucinol microspheres are constructed by in situ growth method. Then, the imine groups of poly (styrene-divinylbenzene)@p-phenylenediamine-1,3,5-triformylphloroglucinol are reduced to amino groups and followed by quaternized. The microspheres are characterized by using SEM, Fourier transform infrared spectra, N2 adsorption-desorption experiment, and so forth. According to the results, poly (styrene-divinylbenzene)@p-phenylenediamine-1,3,5-triformylphloroglucinol microspheres could perfectly combine and possess the good monodispersity of poly (styrene-divinylbenzene) microspheres and unique functionality of p-phenylenediamine-1,3,5-triformylphloroglucinol nanoparticles. The customized column exhibits good separation properties for conventional anions, organic acids, and carbohydrates.

Pioneering the Future: Principles, Advances, and Challenges in Organic Electrodes for Aqueous Ammonium-Ion Batteries

Aqueous ammonium-ion (NH4 +) batteries (AAIBs) have recently been considered as attractive alternatives for next-generation large-scale energy storage systems, on account of their cost-effectiveness, nonflammability, less corrosive, small hydrated ionic radius, and rapid NH4 + diffusion kinetics. In addition, the tetrahedral structure of NH4 + exhibits preferential orientation characteristics, resulting in a different electrochemical storage mechanism from spherical charge carriers such as Li+, Na+, and K+. Therefore, unlocking the NH4 +-ion storage mechanisms in host electrode materials is pivotal to advancing the design of high-performance AAIBs. Organic materials, with their customizable, flexible, and stable molecular structures, along with their ease of recycling and disposal, offer tremendous potential. However, the development of cutting-edge organic electrode materials specifically for ammonium-ion storage in AAIBs remains an exciting, yet largely untapped, frontier. This review systematically explores the interaction mechanisms between NH4 + ions and organic electrode materials, such as electrostatic interactions including hydrogen bonding. It also highlights the application of diverse organic electrode materials, such as small molecules, conducting polymers, covalent organic frameworks (COFs), and organic-inorganic hybrids in AAIBs. Lastly, the review addresses the key challenges and future perspectives of organic-material-based AAIBs, aiming to push the boundaries of cutting-edge aqueous energy storage systems.

Advances in synthetic strategies for two-dimensional conjugated polymers

Two-dimensional conjugated polymers (2D CPs) are typically represented by 2D conjugated covalent organic frameworks (COFs) that consist of covalently cross-linked linear conjugated polymers, which possess extended in-plane π-conjugation and out-of-plane electronic couplings. The precise incorporation of molecular building blocks into ordered polymer frameworks through (semi)reversible 2D polycondensation methodologies enables the synthesis of novel polymer semiconductors with designable and predictable properties for various (opto)electronic, spintronic, photocatalytic, and electrochemical applications. Linkage chemistry lays the foundation for this class of synthetic materials and provides a library for subsequent investigations. In this review, we summarize recent advances in synthetic strategies for 2D CPs. By exploring synthetic approaches and the intricate interplay between chemical structure, the efficiency of 2D conjugation, and related physicochemical properties, we are expected to guide readers with a general background in synthetic chemistry and those actively involved in electronic device research. Furthermore, the discussion will appeal to researchers intrigued by the prospect of uncovering novel physical phenomena or mechanisms inherent in these emerging polymer semiconductors. Finally, future research directions and perspectives of highly crystalline and processable 2D CPs for electronics and other cutting-edge fields are discussed.

Emerging Trends in Conductive Two-Dimensional Covalent Organic Frameworks for Large-Area Electronic Applications

Two-dimensional covalent organic frameworks (2D COFs) are emerging as promising materials for advanced electronic applications due to their tunable porosity, crystalline order, and π-conjugated structures. These properties enable efficient charge transport and bandgap modulation, making 2D COFs strong candidates for electronic devices such as transistors and memristors. However, the practical application of COFs remains limited by challenges in achieving high-quality thin films with large-area uniformity and improved crystallinity. This review explores recent advancements in the fabrication and application of conductive 2D COFs for electronics. Various synthesis strategies, including direct growth, vapor-assisted conversion, and interfacial methods, are discussed in the context of enhancing film quality and scalability. The integration of COFs into electronic devices is classified based on their operation mechanism─planar and vertical field-effect transistors (FETs), electrochemical transistors (ECTs), and memristors─to highlight their electronic properties and device performance. Looking forward, the challenges of large-scale production, material compatibility, and device integration are outlined, alongside potential solutions through innovative synthesis techniques and collaborative research efforts. By addressing these challenges, 2D COFs are poised to drive breakthroughs in electronic devices by their adoption in next-generation semiconducting technologies.

Autocatalytic Interfacial Synthesis of Self-Standing Amide-Linked Covalent Organic Framework Membranes

The synthesis of crystalline covalent organic frameworks (COFs) has in principle relied on reversible dynamic chemistry. A general method to synthesize irreversibly bonded COFs is urgently demanded for driving the COF chemistry to a new era. Here we report a universal two-step method for the straightforward synthesis of irreversibly amide-linked COF (AmCOF) membranes by autocatalytic interfacial polymerization (AIP). Highly crystalline amide and imine bilinker COF (AICOF) membranes are readily synthesized by AIP strategy which ingeniously leverages interfacial polymerization to generate amide units followed by an autocatalytic condensation that forms imine bonds. Then, the fully amide-linked AmCOF membranes with Turing structures can be prepared through irreversible linker renovation. The universality of this method has been exemplified by nine AmCOF membranes. Among them, the AmCOF-1 membrane exhibits superior performance for H2O2 photosynthesis (4353 μmol g-1 h-1) and high stability, enabling continuous production of H2O2 under sunlight for 150 h without sacrificial agents. Mechanistic investigations reveal that the greatly improved properties are attributable to the built-in robust amide knots, facilitating full separation of electrons and holes, ultra-long exciton diffusion length, and fast dissociation of excitons within the AmCOF channels.

Olefin-Linked Covalent Organic Frameworks as Prospective Artificial Platforms for Efficient Photocatalysis

The development of semiconducting materials for photoredox catalysis holds great promise for sustainable utilization of solar energy. Olefin-linked covalent organic frameworks (COFs), which are built by linking organic structs into crystalline frameworks through C=C bonds, have attracted tremendous attention in photocatalysis due to their saliant advantages such as extended π-conjugation, permanent porosity, exceptional chemical stability, light-harvesting and charge separation abilities. This review offers a comprehensive overview of recent new advances toward the development of olefin-linked COFs and their uses as artificial platforms for photocatalytic applications, like hydrogen evolution, carbon dioxide reduction and organic transformations. Structural design strategies, preparation methods and structure-function relationships in various photoredox reactions are summarized, which is accompanied by various approaches to boost their catalytic performance. The challenges and future prospectives are further discussed.

Phenoxazine-based covalent organic frameworks as a turn-off fluorescent probe for trace water detection in organic solvents

Phenoxazine-based COFs (TFPB-DAPO-COF and TFPT-DAPO-COF) were synthesized and exhibited wider characteristic intramolecular charge transfer (ICT) than parent phenoxazine. Phenoxazine-based COFs can form hydrogen bonds with water molecules in aprotic solvents, weakening the ICT effect, and leading to a proportional decrease in fluorescence intensity. Therefore, DAPO-COFs can be used as a tool for the detection of water molecules. Among them, TFPT-DAPO-COF shows faster and higher selective response to water on a molecular level in THF with low detection limit (0.0656% v/v).

Surface Involvement in the Boosting of Chiral Organocatalysts for Efficient Asymmetric Catalysis

Nanostructures with curved surfaces and chiral-directing residues are highly desirable in the synthesis of asymmetric chemicals, but they remain challenging to synthesize without using unique templates due to the disfavored torsion energy of twisted architectures toward chiral centers. Here, a strategy for the facile fabrication of highly cured capsule-shaped catalysts with chiral interiors by the amplification of molecular chirality via the irreversible cross-linking of 2D asymmetric laminates is presented. The key to the success of these irregular 2D layers is the use of hierarchical assembly of chiral macrocycles, which can exactly regulate the cured nanostructures as well as asymmetric catalysis. The cross-linking of 2D laminates from the assembly of hexameric macrocycles with one proline edge gave rise to rarely curled capsules with a diameter of 200-400 nm and excellent enantioselectivities as well as diastereoselectivities for asymmetric aldol reactions (94% ee and 1:13 dr). The tetrameric macrocycles decorated with the chiral block produced further curled porous structures, giving an outstanding enantioselectivities (up to 98% ee and 1:17 dr). The strategy of mechanical surface folding will provide a new insight related to increasing the enantioselectivity of chiral organocatalysts.

Covalent organic frameworks in cancer theranostics: advancing biomarker detection and tumor-targeted therapy

In recent years, covalent organic frameworks (COFs) have garnered considerable attention in the field of onco-nanotechnology as a new type of nanoporous construct due to their promising physicochemical properties, ease of modification, and ability to be coupled with several moieties and therapeutic molecules. They can not only be used as biocompatible nanocarriers to deliver therapeutic payloads to the tumor zone selectively but can also be combined with a variety of therapeutic modalities to achieve the desired treatments. This review comprehensively presented recent achievements and progress in COF-based cancer diagnosis, detection, and cancer therapy to provide a better prospect for further research. Herein our primary emphasis lies on exploring the application of COFs as potential sensors for cancer-derived biomarkers that have received comparatively less attention in previous discussions. While the utilization of COFs in solid tumor therapy has faced significant challenges in scientific research and clinical applications, we reviewed the most promising features that underscore their potential in cancer theranostics.

Industrialization of Covalent Organic Frameworks

Covalent organic frameworks (COFs) have attracted broad interest because of their well-defined, customizable, highly stable, and porous structures. COFs have shown significant potential for various practical applications, such as gas storage/purification, drug purification, water treatment, catalysis, and battery applications. Scaling up COFs is highly desirable to meet industrial application demands but is hindered by the limitations of synthesis methods and the high cost of reactants. Recently, emerging green synthesis methods, such as mechanochemical synthesis and flux synthesis, have offered promising solutions to these challenges (e.g., ton-scale production of COFs has been achieved by companies recently). This Perspective provides an overview of the state of the art with respect to the industrial production of COFs and discusses factors influencing the large-scale production of COFs. Directions and opportunities for improving the performance and sustainability of COFs toward industrial applications are also emphasized.

Rational design of surface termination of Ti3C2T2 MXenes for lithium-ion battery anodes

Two-dimensional transition metal carbides, carbonitrides and nitrides (MXenes) have garnered increasing interest in the energy storage field due to their unique structural and electronic properties. However, the application performance is highly reliant on the surface termination, which is poorly understood from a chemical standpoint. In this work, the structural stability, chemical origin, electronic structure and lithium-ion (Li-ion) storage properties of 15 nonmetal terminated MXenes in the form of Ti3C2T2 (T = B, C, Si, N, P, As, O, S, Se, Te, F, Cl, Br, I and OH) were investigated using first-principles calculations. The results indicate that the partially occupied d-orbital and zero pseudogap lead to the high chemical activity of surface Ti, and that surface terminations can diminish its chemical activity. Furthermore, a large pseudogap of the d-orbital promotes the structural stability of Ti3C2T2. A useful descriptor, the antibonding state (Eσ*), was proposed to predict Li-ion adsorption energy. Combining the good electronic conductivity, high lithophilicity, low Li-ion diffusion barrier and high specific capacity, Ti3C2As2, Ti3C2S2 and Ti3C2Se2 are considered as promising anode candidates for Li-ion batteries. Additionally, S, Se and As doping can improve the Li-ion storage performance of oxygen terminated Ti3C2O2. This work offers insights into the chemical origin of the surface termination and paves the way for designing excellent Li-ion anode candidates based on MXenes.

Superacid In Situ Protected Synthesis of Covalent Organic Frameworks

Covalent organic frameworks, as a class of fascinating crystalline porous materials, are attracting increasing attention in various fields. Synthesizing these materials to attain crystallinity and porosity is essential; however, it is time-consuming, not cost-effective, and energy-demanding as it involves extensive screenings of reaction conditions and employs undesired aromatic solvents. Despite recent progress in the synthesis, finding an efficient, convenient, low-toxicity, and widely applicable method remains a challenging goal. Here, we report an in situ-protected strategy for synthesizing imine-linked frameworks by exploring triflic acid as the catalyst to replace traditional acetic acid and deploying alcohols as a single-component reaction medium instead of aromatic solvents. We found that the function of triflic acid is threefold: it rapidly protonates amino groups of amine monomers into ammonium cations, protects formyl units of aldehyde monomers by converting them into acetals, and improves the solubilities of both monomers. The in situ-protection scheme greatly changes their concentrations and reactivities, making reactions highly controllable and reversible. This strategy is general for various monomer combinations to develop imine-linked frameworks with different topologies, including tetragonal, rhombic, pentagonal, hexagonal, kagome, dual trigonal, dual rhombic, and dual hexagonal shapes, and various pore sizes from micropores to mesopores, presenting a facile and simple way to synthesize 28 different yet high-quality frameworks in n-butanol/water. Remarkably, nine new imine-linked frameworks are synthesized for the first time, which cannot be prepared by traditional systems. The porphyrin frameworks exhibited exceptional photocatalytic activities in the activation of molecular oxygen to produce highly reactive oxygen species of singlet oxygen.

From Fundamentals to Synthesis: Covalent Organic Frameworks as Promising Materials for CO2 Adsorption

Covalent organic frameworks (COFs) are highly crystalline polymers that possess exceptional porosity and surface area, making them a subject of significant research interest. COF materials are synthesized by chemically linking organic molecules in a repetitive arrangement, creating a highly effective porous crystalline structure that adsorbs and retains gases. They are highly effective in removing impurities, such as CO2, because of their desirable characteristics, such as durability, high reactivity, stable porosity, and increased surface area. This study offers a background overview, encompassing a concise discussion of the current issue of excessive carbon emissions, and a synopsis of the materials most frequently used for CO2 collection. This review provides a detailed overview of COF materials, particularly emphasizing their synthesis methods and applications in carbon capture. It presents the latest research findings on COFs synthesized using various covalent bond formation techniques. Moreover, it discusses emerging trends and future prospects in this particular field.

Reticular Synthesis of Covalent Organic Frameworks with kgd-v Topology and Trirhombic Pores

Two-dimensional (2D) covalent organic frameworks (COFs) with designable pore structures can be synthesized under the guidance of topology diagrams. Among the five existing edge-transitive topological nets, kgd topology is considered a fine candidate for constructing COFs with ultramicropores. However, all of the reported COFs with kgd topology need the use of C6-symmetric monomers, which are limited in compound type and difficult to synthesize. Here, we first develop a new approach to construct 2D COFs (clv-COFs) with a similar geometrical shape of kgd topology, named kgd-v topology, through the combination of C2v- and C3-symmetric monomers. The size of micropores in these clv-COFs is consistent with the rhombic pores in kgd topology and can be easily tuned by varying the length of C2v- and C3-symmetric monomers. These clv-COFs exhibit excellent atmospheric water harvesting (AWH) ability due to regular small micropores. An efficient water harvester based on clv-COF-1 can produce 1.73 L kg-1 day-1 at 45% relative humidity under solar illumination. Our approach enriches the reticular chemistry and can facilitate the research of COF-based AWH systems.

Highly Enantioselective Transportation Across Liquid Membranes Mediated by Porous Covalent Organic Frameworks

Chiral liquid membrane separation is crucial in pharmaceuticals and chemical synthesis for its simplicity and stability, yet designing membrane carriers that enable efficient enantioseparation remains a challenge. Here, we demonstrated for the first time that chiral porous materials can act as mobile carriers of bulk liquid membranes (BLMs) to enhance enantioselective transport and separation. We design and prepare three 2D chiral covalent organic frameworks (CCOFs) by imine condensations of a chiral dialdehyde with triamines containing ethyl, fluorine and/or isopropyl groups. These isostructural CCOFs feature ABC stacking, excellent water, acid and base tolerance, and chiral amine groups in 1D porous channels, promoting efficient enantioselective transportation of amino acid enantiomers. Among them, the CCOF with both -F and -iPr groups showing superior transport performance. Exfoliating the CCOF into chiral nanosheets creates flexible layers with accessible active sites, enabling nanosheet-mediated liquid membranes to separate chiral drug enantiomers, a feat unattainable with the pristine CCOF. This work establishes CCOFs as a promising platform for chiral BLM separations and will guide the design of high-performance BLMs using porous materials for enantioselective separation.

Induced Charge-Compensation Effect for Boosting Photocatalytic Water Splitting in Covalent Organic Frameworks

Imine-based covalent organic frameworks (COFs) are promising for photocatalytic water splitting, but their performance is often constrained by inefficient charge separation due to the high electron localization nature of polar imine bonds. In this study, we have optimized the electron delocalization across the imine linkage within a COF by implementing a charge compensation effect. This effect is achieved when a strong electron-donating thieno[3,2-b]thiophene linker is directly attached to the iminic carbon of a zinc-porphyrinic COF. This modification significantly reduces the electron binding effect within the imine bonds of the COF, facilitating both in-plane charge separation and out-plane charge transfer to the catalytic site. Conversely, the use of strong electron-withdrawing pyrizine linker aggravates the electron localization at the imine linkage in the ZnP-Pz variant. Consequently, ZnP-Tt shows a substantially improved photocatalytic water-splitting activity under visible light irradiation, with a hydrogen evolution of 44288±2280 μmol g-1 in 4 h, which exceeds the ZnP-Pz counterpart by a factor of 10. These results offer fresh perspectives for the design of imine-based COFs to overcome their limitations in charge separation efficiency.

Synthesis of single-crystalline sp2-carbon-linked covalent organic frameworks through imine-to-olefin transformation

sp2-carbon-linked covalent organic frameworks (sp2c-COFs) are crystalline porous polymers with repeat organic units linked by sp2 carbons, and have attracted increasing interest due to their robust skeleton and tunable semiconducting properties. Single-crystalline sp2c-COFs with well-defined structures can represent an ideal platform for investigating fundamental physics properties and device performance. However, the robust olefin bonds inhibit the reversible-reaction-based crystal self-correction, thus yielding polycrystalline or amorphous polymers. Here we report an imine-to-olefin transformation strategy to form single-crystal sp2c-COFs. The isolated single crystals display rectangular nanotube-like domains with sizes up to approximately 24 μm × 0.8 μm × 0.8 μm, and permanent pore distribution around 1.1 nm. The highly conjugated olefin linkage endows the crystals with enhanced electronic connectivity which determines a remarkable room-temperature metal-free ferromagnetism (8.6 × 10-3 emu g-1). Our protocol is robust and generally applicable for the synthesis of single-crystalline sp2c-COFs for future spin-electron devices.

Rigidity-Flexibility Regulation and Hard-Soft Donor Combination: Dual Strategies in Covalent Organic Frameworks Construction for Actinides/lanthanides Separation

Separating actinides from lanthanides is essential for managing nuclear waste and promoting sustainable nuclear energy development. The recycling of transuranium elements (TRUs: Np, Pu, Am) is also significant for various nuclear technology applications. In this study, a dual strategy is introduced to designing covalent organic frameworks (COFs) that skillfully combines molecular rigidity with flexibility, integrating both hard and soft donor atoms in the synthesis of monomers. This results in a specialized COF that efficiently and selectively captures TRUs from acidic aqueous solutions. By utilizing the topological arrangement of rigid ligands to influence the twisting and stretching of flexible ligands, coordination environment featuring nitrogen and oxygen is created, which enhances the separation of transuranium in various oxidation states over lanthanides. In 0.5 m HNO3 solution, the as-synthesized DAPhen-COF achieves removal rates of 99.1% for Np(V) and 95.8% for Pu(IV). For Am(III), the removal rate reaches 98.6% in 0.01 m HNO3. DAPhen-COF exhibits remarkable selectivity for Np(V), with a separation factor of over 5000 for Np/Gd, outperforming other solid-phase materials. This research provides a comprehensive investigation into the design and synthesis of COFs for actinide capture, marking the first application of COFs in the separation of various TRUs over lanthanides.

Recent Advance in the Synthesis and Applications of Chiral Covalent Organic Frameworks: A Mini-Review

Chiral covalent organic frameworks (CCOFs) are emerging porous materials with tunable chiral structures, abundant pores, and high surface areas, gaining significant attentions in separation, sensing, and asymmetric catalysis. This review summarizes the synthesis methods of CCOFs and their applications in chiral recognition. It discusses the advantages and limitations of three synthesis strategies, including chiral post-modification, direct synthesis, and chiral-induced synthesis. The review also highlights the potential of CCOFs in chiral separation, sensing, and asymmetric catalysis for efficient purification, detection, and synthesis of chiral molecules. Challenges and future directions for the preparation and application of CCOFs are also addressed, aiming to guide further research and practical applications.

Engineering p-Orbital States via Molecular Modules in All-Organic Electrocatalysts toward Direct Water Oxidation

Oxygen evolution reaction (OER) is an indispensable anode reaction for sustainable hydrogen production from water electrolysis, yet overreliance on metal-based catalysts featured with vibrant d-electrons. It still has notable gap between metal-free and metal-based electrocatalysts, due to lacking accurate and efficient p-band regulation methods on non-metal atoms. Herein, a molecular modularization strategy is proposed for fine-tuning the p-orbital states of series metal-free covalent organic frameworks (COFs) for realizing OER performance beyond benchmark precious metal catalysts. Optimized combination of benzodioxazole/benzodiimide-based building blocks achieves an impressive applied potential of 1.670 ± 0.004 V versus reversible hydrogen electrode (RHE) and 1.735 ± 0.006 V versus RHE to deliver enhanced current densities of 0.5 and 1.0 A cm-2, respectively. Moreover, it holds a notable charge transfer amount (stands for a long service life) within operation period that outperforms all reported metal-free electrocatalysts. Operando differential electrochemical mass spectrometry (DEMS) with isotope labeling identifies the adsorbate evolution mechanism (AEM). A variety of spectroscopic techniques and density functional theory (DFT) calculations reveal that the p-band center of these catalysts can be shifted stepwise to optimize the oxygen intermediate adsorption and lower the reaction energy barrier. This work provides a novel perspective for enhancing the electrocatalytic performance of metal-free COFs.

Emissive Hydrazone-Linked Covalent Organic Frameworks as Highly Sensitive and Selective Sensor for the Hydrazine Detection

Covalent Organic Frameworks (COFs) exhibit a range of exceptional attributes, including notable porosity, outstanding stability, and a precisely tuned π-conjugated network, rendering them highly promising candidates for fluorescence sensors applications. In this study, the synthesis of two emissive hydrazone-linked COFs designed for hydrazine detection is presented. The partially conjugated structure of the hydrazone linkage effectively weakens the fluorescence quenching processes induced by aggregation. Additionally, the incorporation of flexible structural components further reduces conjugation, thereby enhancing luminescent efficiency. Remarkably, these COFs possess a significant abundance of heteroatoms, enabling distinctive interactions with hydrazine molecules, which in turn results in exceptional selectivity and sensitivity for hydrazine detection. The detection limit of these COFs reaches the nanomolar range, surpassing all previously reported COFs, thereby underscoring their superior performance in chemical sensing applications.

Covalent organic frameworks for radioactive iodine capture: structure and functionality

The adsorption of radioactive iodine is a critical concern in nuclear safety and environmental protection due to its hazardous nature and long half-life. Covalent organic frameworks (COFs) have emerged as promising materials for capturing radioactive iodine owing to their tunable porosity, high surface area, and versatile functionalization capabilities. This review provides a comprehensive overview of the application of COFs in the adsorption of radioactive iodine. We begin by discussing the sources, properties, and hazards of radioactive iodine, as well as traditional capture techniques and their limitations. We then delve into the intrinsic structures of COFs, focusing on their porosity, conjugated frameworks, and hydrogen bonding, which are pivotal for effective iodine adsorption. The review further explores various functionalization strategies, including electron-rich COFs, flexible COFs, ionic COFs, COF nanosheets, and quasi-3D COFs, highlighting how these modifications enhance the adsorption performance. Finally, we conclude with an outlook on future research directions and potential applications, underscoring the significance of continued innovation in this field. This review aims to provide valuable insights for researchers and practitioners seeking to develop advanced materials for the efficient capture of radioactive iodine.

Exploring Supramolecular Frustrated Lewis Pairs

Frustrated Lewis pairs (FLPs) have rapidly become one of the key metal-free catalysts for a variety of chemical transformations. Embedding these catalysts within a supramolecular assembly can offer improvements to factors such as recyclability and selectivity. In this review we discuss advances in this area, covering key supramolecular assemblies such as metal organic frameworks (MOFs), covalent organic frameworks (COFs), polymers and macrocycles.

Supramolecularly Built Local Electric Field Microenvironment around Cobalt Phthalocyanine in Covalent Organic Frameworks for Enhanced Photocatalysis

The local electric field (LEF) plays an important role in the catalytic process; however, the precise construction and manipulation of the electric field microenvironment around the active site remains a significant challenge. Here, we have developed a supramolecular strategy for the implementation of a LEF by introducing the host macrocycle 18-crown-6 (18C6) into a cobalt phthalocyanine (CoPc)-containing covalent organic framework (COF). Utilizing the supramolecular interaction between 18C6 and potassium ion (K+), a locally enhanced K+ concentration around CoPc can be built to generate a LEF microenvironment around the catalytically active Co site. The COF with this supramolecularly built LEF realizes an activity of up to 7.79 mmol mmolCo-1 h-1 in the photocatalytic CO2 reduction reaction (CO2RR), which is a 180% improvement compared to its counterpart without 18C6 units. The effect of LEF can be subtly controlled by fully harnessing the K+@18C6 interaction by changing the potassium salts with different counterions. In situ spectroscopy and density functional theory calculations show that the complexation of K+ by 18C6 creates a positive electric field that stabilizes the critical intermediate *COOH involved in CO2RR, which can be tuned by the halide ion-mediated K+@18C6 interaction and hydrogen-bonding interaction, consequently leading to improved catalytic performance to varying degrees.

Coupling Cu2O clusters and imine-linked COFs on microfiltration membranes for fast and robust water sterilization

As bacterial contamination crises escalate, the development of advanced membranes possessing both high flux and antibacterial properties is of paramount significance for enhancing water sterilization efficiency. Herein, an ultrathin layer of TbPa (an imine-linked covalent organic framework) and nanosized Cu2O clusters, sequentially deposited onto polyethersulfone membranes, demonstrate exceptional water flux performance, reaching a permeance level of 16000 LHM bar-1. The deposited TbPa, generating uniformly distributed reduction sites under illumination, facilitates the uniform formation of Cu2O clusters. Furthermore, these anchored Cu2O clusters significantly optimize electron transport within the ultra-thin layer of TbPa, thereby enhancing the performance of the membrane in generating reactive oxygen species (ROS). Consequently, this membrane achieves a flux recovery rate exceeding 98.6% for flux losses caused by bacterial fouling and maintains consistent performance over 10 cycles. This work presents an effective strategy for accessing bactericidal membranes and provides insights into efficient and mild water sterilization.

Integrating Multiple Redox-Active Units into Conductive Covalent Organic Frameworks for High-Performance Sodium-Ion Batteries

The rational design of porous covalent organic frameworks (COFs) with high conductivity and reversible redox activity is the key to improving their performance in sodium-ion batteries (SIBs). Herein, we report a series of COFs (FPDC-TPA-COF, FPDC-TPB-COF, and FPDC-TPT-COF) based on an organosulfur linker, (trioxocyclohexane-triylidene)tris(dithiole-diylylidene))hexabenzaldehyde (FPDC). These COFs feature two-dimensional crystalline structures, high porosity, good conductivity, and densely packed redox-active sites, making them suitable for energy storage devices. Among them, FPDC-TPT-COF demonstrates a remarkably high specific capacity of 420 mAh g-1 (0.2 A g-1), excellent cycling stability (~87 % capacity retention after 3000 cycles, 1.0 A g-1) and high rate performance (339 mAh g-1 at 2.0 A g-1) as an anode for SIBs, surpassing most reported COF-based electrodes. The superior performance is attributed to the dithiole moieties enhancing the conductivity and the presence of redox-active carbonyl, imine, and triazine sites facilitating Na storage. Furthermore, the sodiation mechanism was elucidated through in situ experiments and density functional theory (DFT) calculations. This work highlights the advantages of integrating multiple functional groups into redox-active COFs for the rational design of efficient and stable SIBs.